The Six Nations are investigating the French use of the Head Injury Assessment (HIA) during their defeat to Ireland on Saturday.

Out-half Matthieu Jalibert and replacement scrum-half Antoine Dupont were both taken off after suffering knee injuries, but their replacements were registered as HIAs which provoked controversy with Brian O'Driscoll and Paul O'Connell both questioning the call.

In the case of Dupont, the decision to use a HIA allowed France to re-introduce No. 9 Maxime Machenaud. Had Dupont come off with a non-head or blood injury, the Racing 92 player would not have been allowed back on.

However, Machenaud was not allowed take the kick that Anthony Belleau pulled wide because he had come on as a HIA replacement under the laws.

France claimed both HIAs were ordered by the independent match-day doctor.

Under their existing HIA protocols, Six Nations review each incident that requires an assessment and they will await the findings of that review before proceeding.

"As part of that protocol, there is a process by which HIA/concussion-related incidents are reviewed," a statement read.

"This involves an initial review by an independent HIA Review Processor, Alligin (UK) Limited, and then in certain cases a further review by an HIA Review Panel.